Photographic silver halide emulsions with increased sensitivity

ABSTRACT

Photographic silver halide emulsions having increased sensitivity, containing as a chemical sensitizer, an S-alkyldithianium salt and a process for developing photographic silver halide emulsions in the presence of such a salt.

United States Patent [72] Inventors Harald Huckstadt Cologne-Stammheim; Wilhelm Saleck, Schildgen, Bergisch; August Randolph, Leverkusen; Edwin Ranz, Leverkusen, all of Germany [21 Appl. No. 802,654

[22] Filed Feb. 26, 1969 [45] Patented Nov. 23, 1971 [73] Assignee Agfa-Gevaert Aktiengesellschaft Leverkusen, Germany [32] Priority Apr. 26, 1968 [3 3] Germany [52] US. Cl 96/65,

[51] Int. Cl G036 I/28, G03c 5/24 [50] Field ofSearch 96/107, 65

[56] References Cited UNITED STATES PATENTS 2,728,668 12/1955 Mochel 96/107 3,113,026 12/1963 Sprung 96/107 3,471,296 10/1969 Huckstadt ct al 96/107 Primary Examiner-Norman G. Torchin Assistant Examiner-Richard E. F ichter Attorneys-Walter G. Hensel, Walter C. Kehm and Samson B.

Leavitt ABSTRACT: Photographic silver halide emulsions having increased sensitivity, containing as a chemical sensitizer, an S- alkyl-dithianium salt and a process for developing photographic silver halide emulsions in the presence of such a salt.

PHOTOGRAPHIC SILVER HALIDE EMULSIONS WITH INCREASED SENSITIVITY The present invention relates to a method of increasing the speed of photographic silver-halide emulsions by the addition of heterocyclic onium compounds having thioether groups.

The speed of a photographic emulsion can be controlled in two different manners. First of all, it is possible upon the so called chemical ripening during the preparation of the emulsion to increase the speed by increasing the time of ripening or the by addition of suitable substances such as thiosulfate or other preparations, generally containing sulfur. The other manner of increasing the speed of a photographic emulsion consists in adding so-called development accelerators or chemical sensitizers. They are generally added to the emulsion after it has been completely ripened.

As development accelerators, there have been described in this connection, for instance, compounds having an onium structure (such as, for instance, quartemary ammonium, phosphonium, and ternary sulfonium salts) and also very frequently polyalkylene oxide derivatives. Specifically in the case of the last-mentioned type of substance, many attempts have been made to increase the gain in speed obtained by modifying the derivatives or by combined use together with other compounds. None of these compounds, however, fully have the properties required in practical use either because the increase in speed is unsatisfactory or because the fog inherent in the sensitizing prevents use.

The object of the present invention is to provide new chemi cal sensitizers which do not have the above-mentioned drawbacks and by means of which it is possible to increase the speed of photographic silver-halide emulsions without causing an undesired fogging.

lt has now been found that particularly great gains in speed with only relatively slight increase in fog can be obtained by adding to the emulsion quartemary salts of the general formula:

1 I s s -omoa on 01 s s oH,-coo11 Br The preparation of the compounds to be used in the manner of the invention is already known. Reference may be had to the following publications: J. Chem. Soc. (1931), p. 23 I; Vol. 32 (1899 pp. 2,892 et seq.; J. Org. Chem. ll (1946 pp. 704 et seq.

The substances of the invention can be added to the photographic emulsion in any stage of its preparation before, during, or after the chemical ripening. They can also be added to the coating solution directly before the pouring. The quantity added depends upon the effect desired and can be determined by ordinary tests by a man skilled in the art any time.

In general, quantities of 0.003 to 20 g. and preferably 0.003 to 6 g., per mol of silver halide are sufficient.

The compounds can also be added to the photographic developer. In this case, the same quantities are used as for addition to the emulsion, referred to l liter of developer.

The substances in accordance with the invention can be employed in any desired silver-halide emulsions. As silver halide, silver chloride, silver bromide or mixtures thereof, possibly with a small amount of silver iodide of up to 10 mol percent are suitable. The silver halides can be dispersed in the ordinary hydrophilic compounds, for instance in carboxy methyl cellulose, pholyvinyl alcohol, polyvinyl pyrrolidone, alginic acid and their salts, esters or amides, or preferably gelatin.

The emulsions can also contain other chemical sensitizers, for instance, quaternary ammonium and phosphonium as well as ternary sulfonium salts, reducing agents such as stannous salts, polyamides such as diethylene triamine or sulfur compounds such as described in US. Pat. No. 1,574,944. For the chemical sensitizing, the emulsions indicated may also contain salts of noble metals such as ruthenium, rhodium, palladium iridium, platinum or gold, as has been described in the article by R. Koslowsky in Z. Wiss. Phot. 46, 65-72 I951 The emulsions can furthermore also contain polyalkylene oxides or polyalkylene oxide derivatives as development accelerator or chemical sensitizers.

The emulsions can also be optically sensitized, for instance with the customary polymethine dyes such as neutrocyanines basic or acid carbocyanines, rhodacyanines, hemicyanines, styryl dyes, oxonols and the like. Such sensitizers are described in the book by F .M. Hamer, The Cyanine Dyes and Related Compounds 1964 The emulsions can contain the customary stabilizers such as homopolar or saltlike compounds of mercury with aromatic or heterocyclic rings (for instance mercaptotriazols), simple mercury salts, sulfonium mercury double salts and other mercury compounds. As stabilizers, azaindenes, preferably tetraor pentaazaindenes, and particularly those which are substituted with hydroxyl or amino groups are also suited.

Such compounds are described in an article by Birr in Z. Wiss. Phot. 47, 2-58 (1952 Other suitable stabilizers are, inter alia, heterocyclic mercapto compounds, for instance, phenyl mercaptotetrazol, quaternary benthiazol derivatives, banztriazol, and the like.

The emulsions can be hardened in the customary manner, for instance, with formaldehyde or halogen-substitued aldehydes which contain a carboxyl group such as mucobromic acid, diketones, methane sulfonic acid ester, dialdehydes, and the like.

The substances of the invention possess their advantageous effect not only in black-white emulsions and developers but also in the preparation of colored photographs. In this case they can be added both to photosensitive emulsions which contain color couplers and to color developers.

EXAMPLE 1 liter, 60 g. of silver in the form of silver halide with a content of silver iodide of 6 mol percent was treated with:

600 mg. saponin as wetting agent 200 mg. 4-hydroxy-6-methyl-1,3,3a, 7-tetraazaindene as stabilizer, and

l0 ml. of a 10 percent aqueous solution of formaldehyde as hardening agent.

The emulsion was divided into five equal portions and the following substances (referred to 1 liter of emulsion) added to the individual portions:

Sample A: comparison sample-no addition Sample B: 600 mg. of substance ll Sample C: 600 mg. of substance lll Sample D: 600 mg. of substance lV Sample E: 600 mg. of substance V A silver bromide-iodide-gelatin emulsion containing, per" The coating solutions were poured onto a substrate of cellulose triacetate, exposed in a sensitometer behind a gray step wedge and developed for 10 minutes in a developer having the potassium bromide 2.0 g. made up to one liter The other processing baths had the following composition:

following composition: stop bath: sodium acetate 30.0 g.

O-N-(B-hydroxy ethyl)-aminophenol 10 g. 5 lati a ti agid 6 sodium Sulfile 100 8- made up with water to 1 liter Sodium Carbonate sicc' l0 8- bleaching bath: potassium ferricyanide 100 g. made up to 1 liter with water: I g. potassium id 20 glatial acetic acid 4 g. TABLE 1 10 made up with water to 1 liter fixing bath: sodium thiosulfate 200 g. Sample E- 7 5 made up with water to 1 liter The color density of the magenta layers were measured with A w 0 46 0 m 5 a Macbath Quanta Log, Model TD [02 densitometer using 8 green color filter 1n the path of the measuring l1ght. c +1.s 0.43 0.00 D +1.0 0.43 0.11 TABLE 2 E +2.7= 0.45 0.08

SAMPLE E 7 s An increase of 3 means twice the sensitivity or an increase in sensitivity (speed) of one stop. EXAMPLE 2 A typ. 0.53 0.18 A mixed emulsion composed of 90 percent of a silver-bro- B +3.0 0.49 0.10 mide-iodide gelatin and 10 percent of a silver-chloride-bro- 3 5: 3:; 3 mide-iodide emulsion and which was ripened in known E manner with gold and sulfur compounds until optimum sen- F 049 016 sitivity was obtained was treated with 45 mg./kd. of emulsion G +1.9 0.50 0.15 of the sensitizing dyestufiof the following formula: H

\ I An increase of 3 means twice the sensitivity or an increase C CH=C CH=C in sensitivity of one stop. Br We claim: I GB f I l. Light-sensitive photographic element having a silver haa a OZHI lide emulsion layer containing as a chemical sensitizer a sensitizing amount of a dithianium salt having one of the follow- There was furthermore added to each liter of the emulsion: ing formulas: l5 g. l'-sulf0-4'-phenoxy)-phenyl-3-hepta-decyl- GH -CH pyrazolone as magenta coupler 4 6 250 mg. 1,3,3a, 7-4-hydroxy--methyl-tetrazaindene as sta- S X bilizer CH CH 20 ml. of a 5 percent aqueous solution of saponin as wetting agent 2 2 2.5 ml. of a 30 percent aqueous solution of formaldehyde as S R-Z e hardening agent. \OHPCHZ The above emulsion was divided into 10 equal portions and 7 the substances set forth in the following table (referred to 1 wherein R represents an alkyl group containing up to l2 carli r Of emulsion) added to the individual Portions: bon atoms, Y represents a member selected from the group Sample A! comparison SamPlefl0 addition consisting of hydrogen and monovalent substituents, X

Sample B: 300 mg. ofsubstance] Sample C: l.0 g. ofsubstance l Sample D: 3.0 g. of substance I Sample E: 300 mg. of substance lll Sample F: 300 mg. ofsubstance lV Sample G: 1.0 g. ofsubstance IV Sample H: 3.0 g. ofsubstance lV The samples were poured onto a substrate of cellulose acetate and dried. Thereupon they were exposed behind a step wedge and processed in customary manner. The course of the processing was as follows:

color development stop bath 5 minutes washing 5 minutes bleaching bath 5 minutes washing 5 minutes fixing bath 5 minutes washing 10 minutes The color developer has the following composition: diethyl-p-phenylene diamine-sulfate 2.75 g. hydroxyl amine sulfate 1.2 g. sodium silfite sicc. 2.0 g. sodium hexametaphosphate potassium carbonate sicc.

7 minutes represents an anion. and Z represents a monovalent anionic salt-formin g substituent.

2. Light-sensitive photographic element according to claim 1 wherein said chemical sensitizer has the following formula:

5 s cH,'oH,.oH c1- era-0H,

011 011. Q s\ s cH,-cooH Br- GHQ-70H;

4. Light-sensitive photographic element according to claim 1, wherein said chemical sensitizer has the following formula:

/CH1-CHZ ea s s-om-c o o 9 5. Light-sensitive photographic element according to claim 1, wherein said chemical sensitizer the following formula:

CH,CH,

7. Light-sensitive photographic element according to claim I, wherein said chemical sensitizer has the following formula:

/CH CH 9 s S-CH1CH3 01o 8. A process for preparation of photographic images wherein an imagewise-exposed silver halide photographic layer is developed with a silver halide developing agent in the presence of a sensitizing amount of a dithianium salt having one of the following fonnulas:

wherein R represents an alkyl group containing up to 12 carbon atoms, Y represents a member selected from the group consisting of hydrogen and monovalent substituents, X represents an anion, and Z represents a monovalent anionic salt-forming substituent. 

2. Light-sensitive photographic element according to claim 1, wherein said chemical sensitizer has the following formula:
 3. Light-sensitive photographic element according to claim 1, wherein said chemical sensitizer has the following formula:
 4. Light-sensitive photographic element according to claim 1, wherein said chemical sensitizer has the following formula:
 5. Light-sensitive photographic element according to claim 1, wherein said chemical sensitizer has the following formula:
 6. Light-sensitive photographic element according to claim 1, wherein said chemical sensitizer has the following formula:
 7. Light-sensitive photographic element according to claim 1, wherein said chemical sensitizer has the following formula:
 8. A process for preparation of photographic images wherein an imagewise-exposed silver halide photographic layer is developed with a silver halide developing agent in the presence of a sensitizing amount of a dithianium salt having one of the following formulas: 